1. Field of the Invention
This invention relates to a vibrating screen mechanism and, more particularly, to a vibrating screen mechanism that is used to separate materials by size.
2. Background of the Invention
For many years, vibrating screens have been used to separate products into different sizes. While some screens may be used in an environment that is relatively mild, other screens would be used in the harshest of environments, such as mines, quarries or plants, where materials, such a bauxite, gravel, crushed rock, limestone, cement, shale or clay, are sized into different sizes. In these harsh environments in which a vibrating screen operates, any mechanically moving parts can be fouled by dust, grit or grime from the materials being sized. The larger number of moving parts to operate the vibrating screen, the greater the probability there will be a mechanical failure. The simpler the operation of the vibrating screen, the less likely the mechanical parts will foul or break.
U.S. Pat. No. 4,444,656 to Nelson shows a vibrating screen with a plurality of transverse beams extending from side to side for vibrating the screen. A large number of beams are used, as well as a large number of moving parts. Likewise, a plurality of different motors are used, with each transverse beam having a different motor and a different rate of vibration.
Typical of the modern day vibrating screen are those screens disclosed in U.S. Pat. Nos. 3,378,142; 3,834,534; 4,180,458; 4,274,953; 4,340,469; 4,632,751; 5,100,539; 5,341,939; and 5,749,471. Unlike the present invention, in each of the referenced patents, a motor is attached to a frame to which is attached a screen. Activation of the motor causes the frame and consequently, the screen to vibrate. To allow such vibration, the frame is somehow affixed to isolating devices, usually springs. U.S. Pat. No. 3,378,142 imparts the vibrating force to the frame using xe2x80x9ctwo drivingly coupled resiliently borne oscillating frames having alternative inter-engaging cross members.xe2x80x9d U.S. Pat. No. 3,834,534 attaches a screen to a frame using springs and then allows the vibration mode of the screen and frame assembly to be controlled as well as slid beneath the screen. U.S. Pat. No. 4,180,458 uses a traditional structure, but isolates the structure to achieve better noise control. U.S. Pat. No. 4,274,953 mounts the vibration motor on the outside of the frame. U.S. Pat. No. 4,340,469 imparts the vibrational force to the frame and screen using unbalanced weights to generate gyrational vibratory motion. U.S. Pat. Nos. 4,632,751; 5,100,539; 5,341,939; and 5,749,471 each contain disclosures typical of vibrating frame/screens. Unlike the present invention, all of the inventions disclosed in the foregoing patents contain complex vibrating mechanisms with multiple mechanical parts and the vibrating force is imparted to a frame which in turn causes the screen to vibrate.
Not known to be the subject of a U.S. patent, is the vibrating screen apparatus utilized by JandH Equipment, Inc. (xe2x80x9cJandHxe2x80x9d), P.O. Box 928, Roswell, Ga. 30077, telephone number (800) 989-1606. Unlike the present invention which does not attach the vibrating screen apparatus to the screen and which does not require attachment through the screen, the JandH vibrating screen apparatus attaches rods across and through a screen. The rods are then attached to an overhead motor which, when activated, unlike the present invention, causes the entire apparatus, screen rods and screen to vibrate.
To simply and advance the prior art, a vibrating screen apparatus must, as does the present invention, reduce the number and complexity of the mechanical parts necessary to cause vibration of the screen and which in fact vibrate. Furthermore, for ease of maintenance, the entire vibrating apparatus should easily remove from the screen system.
It is an object of the present invention to provide a vibrating screen apparatus with a minimum amount of moving parts.
It is a further object of the present invention to provide a vibrating screen apparatus that is easily maintained and repaired.
It is yet another object of the present invention to provide a vibrating screen apparatus that is more reliable and economical to operate.
It is an even further object of the present invention to provide a vibrating screen apparatus that has less dust pollution or noise proliferation.
It is yet another object of the present invention to have vibrating bars that run lengthwise of the screen to impart the necessary vibrations to the screen.
It is yet another object of the present invention to suspend the vibrating bars and pull the screen taut by inflating air mounts below the vibrating bars.
It is yet another object of the present invention to provide tension rails for proper tensioning of the wire cloth that makes up the vibrating screen.
It is even another object of the present invention to mount the vibrating motor to the vibrating bars to cause the vibration of the wire cloth of the vibrating screen apparatus.
In the present invention, side plates are held into position by cross braces to form the frame of the present vibrating screen apparatus. The bottom of the frame is enclosed by a concave surface and a discharge outlet for the fine material that has gone through the last screen.
The screen is made of wire cloth that is tightened by tension rails on each side. The tension rails connect into hooks that are attached to the wire cloth and pulled tight between the respective sides of the frame.
Immediately below the screen are vibrating bars that run lengthwise of the screen. Attached to the underside of the vibrating bars is a vibrating motor that will cause the bars to vibrate. On top of the vibrating bars is some type of resilient material, such as rubber, to keep the vibrating bars from wearing out the screen.
The vibrating bars are mounted on air mounts set on cross braces between the sides of the frame. By inflating the air mounts, the screen is tightened to the predetermined tautness that is desired when the vibrating bar is lifted. Tension on the wire cloth increased and the vibrating mechanism is ready to be turned ON for operation.
Material to be sized comes in at the feed end of the vibrating screen apparatus. Material that is less than the predetermined size of the wire cloth will go through the screen and be less than the predetermined size. The remainder of the material that is larger than the predetermined size will come out of the discharge end of the vibrating screen apparatus.
If material is to be sized between a predetermined range, vibrating screen apparatuses can be stacked one on top of the other and material that comes out of the discharge end of other than the top vibrating screen apparatus would be of a predetermined size range depending upon the size of the individual screens therebetween.
To prevent air pollution by dust and other particles, a cover will cover the uppermost of the vibrating screen apparatuses. In the present invention, a rubber dust cover is used that is ratcheted down tightly into place to prevent noise proliferation or environmental pollution by dust.
Since the entire vibrating screen apparatus is gravity fed, the angle of the frame should be at least greater than the angle of repose of the material being sized. It is anticipated the angle of repose would typically be between 15xc2x0-45xc2x0.